Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;

int main() {
  using pii = pair<int,int>;
  int H, W;
  cin >> H >> W;
  char s[H][W];
  int d[H][W];
  int dy[4]={0,1,0,-1}, dx[4]={1,0,-1,0};
  int w=0;
  for(int i=0;i<H;i++) {
    for(int j=0;j<W;j++) {
      cin >> s[i][j];
      if(s[i][j]=='.') w++;
      d[i][j]=-1;
    }
  }
  queue<pii> que;
  que.push(pii(0,0));
  d[0][0]=1;
  while(que.size()) {
    pii p=que.front();
    que.pop();
    if(p==pii(H-1,W-1)) break;
    for(int i=0;i<4;i++) {
      int ny=p.first+dy[i], nx=p.second+dx[i];
      if(0<=ny&&ny<H&&0<=nx&&nx<W&&s[ny][nx]=='.'&&d[ny][nx]==-1) {
        que.push(pii(ny,nx));
        d[ny][nx]=d[p.first][p.second]+1;
      }
    }
  }
  if(d[H-1][W-1]!=-1) cout << w-d[H-1][W-1] << endl;
  else cout << -1 << endl;
}